Toroidal type continuously variable transmission

ABSTRACT

In a toroidal type continuously variable transmission, first pivot shafts provided on both ends of first trunnions are supported within support holes formed in yokes secured to an inner surface of a casing. The support portions are provided with ball splines and radial needle bearings. During operation, loads acting on the first trunnions are cancelled within the yokes. Axial displacements and rocking displacements of the first trunnions are effected smoothly by the ball splines and the radial needle bearings.

BACKGROUND OF THE INVENTION

1. Field of the Invention

A toroidal type continuously variable transmission according to thepresent invention is used, for example, as a speed change unit of atransmission of a motor vehicle or transmissions of various industrialmachines, respectively.

2. Related Background Art

It has been investigated that a toroidal type continuously variabletransmission schematically shown in FIGS. 24 and 25 is used as atransmission of a motor vehicle. For example, as disclosed in JapaneseUtility Model Laid-Open No. 62-71465 (1987), in such a toroidal typecontinuously variable transmission, an input disc 2 is supported incoaxial with an input shaft 1 and an output disc 4 is secured to an endof an output shaft 3 disposed in coaxial with the input shaft 1. Withina casing (described later in connection with FIGS. 26 to 28) containingthe toroidal type continuously variable transmission, there are providedtrunnions 7 rockable around pivot shafts 6.located at positions twistedwith respect to the input shaft 1 and the output shaft 3.

That is to say, each trunnion 7 is provided at its both end outersurfaces with the pivot shafts 6 in coaxial with each other.Accordingly, the pivot shafts 6 do not intersect with center lines ofthe discs 2, 4 but extend in perpendicular to such center lines.Further, central portions of the trunnions 7 support proximal ends ofdisplacement shafts 8 so that inclination angles of the displacementshafts 8 can be adjusted by rocking or swinging the trunnions 7 aroundthe pivot shafts 6. Power rollers 9 are rotatably supported around thedisplacement shafts 8 supported by the trunnions 7. The power rollers 9are interposed between the input disc 2 and the output disc 4. Innersurfaces 2 a, 4 a of the discs 2, 4 which are opposed to each other haveconcave surfaces obtained by rotating arcs having centers on the pivotshaft 6 around the input shaft 1 and the output shaft 3. Peripheralsurfaces 9 a of the power rollers 9 having spherical convex shapes abutagainst the inner surfaces 2 a, 4 a. A pressing device 10 of loading camtype is disposed between the input disc 2 and the output disc 4 so thatthe input disc 2 is can be urged elastically toward the output disc 4 bythe pressing device 10. The pressing device 10 comprises a cam plate 11rotated together with the input shaft 1, and a plurality (for example,four) of rollers 13 held by a holder 12. One side surface (left sidesurface in FIGS. 24 and 25) of the cam plate 11 is constituted as a camsurface 14 having unevenness or undulation extending along acircumferential direction, and an outer surface (right side surface inFIGS. 24 and 25) of the input disc 2 has a similar cam surface 15. Theplurality of rollers 13 are rotatably supported for rotation around axesextending radially with respect to the center line of the input shaft 1.

In use of the toroidal type continuously variable transmission havingthe above-mentioned construction, when the cam plate 11 is rotated asthe input shaft 1 is rotated, the plurality of rollers 13 are urgedagainst the cam surface 15 formed on the outer surface of the input disc2 by the cam surface 14. As a result, the input disc 2 is urged againstthe plurality of power rollers 9, and, at the same time, due to thefrictional engagement between the pair of cam surfaces 14, 15 and theplurality of rollers 13, the input disc 2 is rotated. Rotation of theinput disc 2 is transmitted to the output disc 4 through the pluralityof power rollers 9, thereby rotating the output shaft 3 secured to theoutput disc 4.

In a case where a rotational speed ratio (speed change ratio) betweenthe input shaft 1 and the output shaft 3, when deceleration is effectedbetween the input shaft 1 and the output shaft 3, the trunnions 7 arerocked or swung around the pivot shafts 6 in predetermined directions,thereby including the displacement shafts 8 so that the peripheralsurfaces 9 a of the power rollers 9 abut against a portion of the innersurface 2 a of the input disc 2 near the center and a portion of theinner surface 4 a of the output disc 4 near its outer periphery,respectively, as shown in FIG. 24. On the other hand, when accelerationis effected, the trunnions 7 are rocked around the pivot shafts 6 inopposite directions, thereby inclining the displacement shafts 8 so thatthe peripheral surfaces 9 a of the power rollers 9 abut against aportion of the inner surface 2 a of the input disc 2 near its outerperiphery and a portion of the inner surface 4 a of the output disc 4near the center, respectively, as shown in FIG. 25. If the inclinationangles of the displacement shafts 8 are selected to an intermediatevalue between FIG. 24 and FIG. 25, an intermediate speed change ratiocan be obtained.

When the actual transmission of the motor vehicle is constituted by theabove-mentioned the toroidal type continuously variable transmission, itis well known in the art to provide a so-called toroidal typecontinuously variable transmission of double cavity type in which twosets of input disc 2, output disc 4 and power rollers 9 are prepared,and such two sets of input disc 2, output disc 4 and power rollers 9 arearranged in parallel to each other along a power transmitting direction.FIGS. 26 and 27 show an example of such a toroidal type continuouslyvariable transmission of double cavity type disclosed in Japanese PatentPublication No. 8-23386 (1996).

An input shaft la is supported within a casing 5 for only rotation. Acylindrical transmission shaft 16 is rotatably supported around theinput shaft 1 a in coaxial with the latter for rotation relative to theinput shaft 1 a. First and second input discs 17, 18 corresponding tofirst and second outer discs of the present invention are supported onboth ends of the transmission shaft 16 via ball splines 19 so that innerfaces 2 a of these discs are opposed to each other. Accordingly, thefirst and second input discs 17, 18 are rotatably supported within thecasing 5 in coaxial with and in synchronous with each other.

Further, first and second output discs 20, 21 corresponding to first andsecond inner discs of the present invention are supported around anintermediate portion of the transmission shaft 16 via a sleeve 22. Anoutput gear 23 is integrally formed on an outer peripheral surface of anintermediate portion of the sleeve 22, and the sleeve has an innerdiameter greater than an outer diameter of the transmission shaft 16.The sleeve is rotatably supported by a support wall 24 provided withinthe casing 5 via a pair of bearings 25 in such a manner than the sleeveis disposed in coaxial with the transmission shaft 16 and can merely berotated. In this way, the first and second output discs 20, 21 arespline-connected to both end of the sleeve 22 rotatably mounted aroundthe intermediate portion of the transmission shaft 16 in a conditionthat inner surfaces 4 a of the discs 20, 21 are directed toward oppositedirections. Accordingly, the first and second output discs 20, 21 aresupported in coaxial with the first and second input discs 17, 18 andare rotated independently from the first and second input discs 17, 18in a condition that the inner surfaces 4 a are opposed to the respectiveinner surfaces 2 a of the first and second input discs 17, 18.

Further, two pair of yokes 26 a, 26 b are supported by an inner wall ofthe casing 5 at both sides of the first and second output discs 20, 21with the interposition of these output discs 20, 21. The yokes 26 a, 26b correspond to yokes constituting first and second supporting means ofthe present invention and are formed as rectangular frames,respectively, by press-working a metal plate such as a steel or forgingmetal material such as steel. The yokes 26 a, 26 b are provided at theirfour corners with circular support holes 31 for rockably supportingfirst and second pivot shafts 29, 30 provided on both ends of first andsecond trunnions 27, 28 (described later) and are also provided withcircular locking holes 32 formed in central portions of the yokes in awidth-wise direction (left-and-right direction in FIGS. 27 and 28)thereof at both ends of the transmission shaft 16 in an axial direction(left-and-right direction in FIG. 26) thereof. The pairs of yokes 26 a,26 b each having the above-mentioned configuration are supported bysupport ports 33 a, 33 b formed on opposed portions of the inner wall ofthe casing 5 for slight displacement. The support posts 33 a, 33 b areopposed to each other and are disposed within a first cavity 34 betweenthe inner surface 2 a of the first input disc 17 and the inner surface 4a of the first output disc 20 and a second cavity 35 between the innersurface 2 a of the second input disc 18 and the inner surface 4 a of thesecond output disc 21. Accordingly, in a condition that the yokes 26 a,26 b are supported by the support posts 33 a, 33 b, one ends of theyokes 26 a, 26 b are opposed to an outer peripheral portion of the firstcavity 34 and the other ends are opposed to an outer peripheral portionof the second cavity 35.

Further, a pair of first trunnions 27 are disposed within the firstcavity 34 at diametrically opposed positions of the first input disc 17and the first output disc 20, and a pair of second trunnions 28 aredisposed within the second cavity 35 at diametrically opposed positionsof the second input disc 18 and the second output disc 21. As shown inFIG. 27, the four (in total) first pivot shafts 29 which are coaxiallyprovided on both ends of the trunnions 27 (two in each trunnion) aresupported by one ends of the pair of yokes 26 a, 26 b for rockingmovement and axial displacement. That is to say, the first pivot shafts29 are supported within the support holes 31 formed in one ends of theyokes 26 a, 26 b via radial needle bearings 36. Each of the radialneedle bearings 36 has an outer race 37 having a spherical convex outerperipheral surface and a cylindrical inner peripheral surface, and aplurality of needles 38. Accordingly, the first pivot shafts 29 aresupported at both axial sides on one ends of the yokes 26 a, 26 b forreversible rocking movement and axial displacement. Further, as shown inFIG. 28, the four (in total) second pivot shafts 30 which are coaxiallyprovided on both ends of the second trunnions 28 (pair in each trunnion)are supported within the second cavity 35 in the same manner as thefirst pivot shafts 29 provided on the first trunnions 27.

The first and second trunnions 27, 28 supported within the casing 5 forrocking movements and displacements in axial directions of first andsecond pivot shafts 29, 30 in this way are provided at theirintermediate portions with circular holes 39, as shown in FIGS. 27 and28. The first and second displacement shafts 40, 41 are supported inthese circular holes 39. The first and second displacement shafts 40, 41have support shaft portions 42 parallel with and eccentric with eachother, and pivot shaft portions 43. The support shaft portions 42 arerotatably supported within the circular holes 39 via radial needlebearings 44. Further, first and second power rollers 45, 46 arerotatably supported around the pivot shaft portions 43 via other radialneedle bearings 47.

Incidentally, the pair of first and second displacement shafts 40, 41provided for each of the first and second cavities 34, 35 are disposedat opposite directions (diametrically opposed at 180 degrees) withrespect to the input shaft 1 a and the transmission shaft 16 for each ofthe first and second cavities 34, 35. Further, directions along whichthe pivot shaft portions 43 of the first and second displacement shafts40, 41 are offset (eccentric) from the support shaft portions 42 are thesame (up-and-down opposite directions in FIGS. 27 and 28) with respectto the rotational direction of the first and second input and outputdiscs 17, 18, 20, 21. Further, the eccentric directions aresubstantially perpendicular to an installation direction of the inputshaft 1 a. Accordingly, the first and second power rollers 45, 46 aresupported for slight displacement in the installation direction of theinput shaft 1 a and the transmission shaft 16 (slight axialdisplacement). As a result, if the first and second power rollers 45, 46tend to be displaced in the axial direction of the input shaft 1 a andthe transmission shaft 16 (left-and-right direction in FIG. 26, and,direction perpendicular to the planes of FIGS. 27 and 28) by change inelastic deformation amount of constructural parts due to fluctuation intorque to be transmitted by the toroidal type continuously variabletransmission, such displacement can be absorbed without acting anyexcessive stress on the constructural parts.

Further, between outer surfaces of the first and second power rollers45, 46 and inner surfaces of intermediate portions of the first andsecond trunnions 27, 28, there are provided, in order from the outersurfaces of the first and second power rollers 45, 46, thrust ballbearings 48, and thrust bearings 49 such as sliding bearings or needlebearings. The thrust ball bearings 48 serve to support thrust loadacting on the first and second power rollers 45, 46 and to allowrotations of the first and second power rollers 45, 46. Further, thethrust bearings 49 serve to support thrust loads acting on outer races50 of the thrust ball bearings 48 and to allow the pivot shaft portions43 and the outer races 50 to rock around the support shaft portions 42.

Further, drive rods 51 are connected to one ends (lower ends n FIGS. 27and 28) of the first and second trunnions 27, 28, and drive pistons 52are secured to outer surfaces of intermediate portions of the drive rods51. The drive pistons 52 are slidably mounted within drive cylinders 53in an oil-tight fashion. The drive pistons 52 and the drive cylinders 53constitute actuators for displacing the first and second trunnions 27,28 along the axial directions of the first and second pivot shafts 29,30. Further, pressurized oil can be supplied within the drive cylinders53 in response to switching of a control valve (not shown).

Further, an pressing device 10 of loading cam type is disposed betweenthe input shaft 1 a and the first input disc 17. The pressing device 10includes a cam plate 11 spline-connected to the intermediate portion ofthe input shaft 1 a so that it can be rotated together with the inputshaft 1 a but cannot be displaced in the axial direction, and aplurality of rollers 13 rotatably held by a holder 12. When the inputshaft 1 a is rotated, the pressing device serves to rotate the firstinput disc 17 while urging it toward the second input disc 18.

When the toroidal type continuously variable transmission having theabove-mentioned construction is driven, the rotation of the input shaft1 a is transmitted to the first input disc 17 through the pressingdevice 10, so that the first and second input discs 17, 18 are rotatedin synchronous with each other. The rotation of the first and secondinput discs 17, 18 is transmitted to the first and second output discs20, 21 through the pairs of first and second power rollers 45, 46disposed within the first and second cavities 34, 35. The rotation ofthe first and second output discs 20, 21 is picked-up by the output gear23. When the rotational speed ratio between the input shaft 1 a and theoutput gear 23 is changed, by switching the control valve, the pairs ofdrive pistons 52 corresponding to the first and second cavities 34, 35are displaced in opposite directions by the same distance for thecavities 34, 35, respectively.

When the drive pistons 52 are displaced, two pairs (four in total) oftrunnions 27, 28 are displaced in opposite directions, so that, forexample, the first and second power rollers 45, 46 at the right in FIGS.27 and 28 are shifted downwardly (FIGS. 27 and 28) and the first andsecond power rollers 45, 46 at the left in FIGS. 27 and 28 are shiftedupwardly (FIGS. 27 and 28). As a result, directions of tangential forcesacting on the contact areas between the peripheral surfaces 9 a of thefirst and second power rollers 45, 46 and the inner surfaces 2 a, 4 a ofthe first and second input discs 17, 18 and the first and second outputdiscs 20, 21 are changed. As the directions of forces are changed, thefirst and second trunnions 27, 28 are rocked in opposite directionsaround the first and second pivot shafts 29, 30 supported by the yokes26 a, 26 b. As a result, as shown in FIGS. 24 and 25, the contact areasbetween the peripheral surfaces 9 a of the first and second powerrollers 45, 46 and the inner surfaces 2 a, 4 a of the discs 17, 18, 20,21 are changed, thereby changing the rotational speed ratio between theinput shaft 1 a and the output gear 23.

By the way, in the conventional arrangement shown in FIGS. 26 to 28, thefirst and second trunnions 27, 28 are supported within the casingthrough the support posts 33 a, 33 b and the yokes 26 a, 26 b. Thus,since the number of parts is increased, not only manufacture, controland assembling of the parts become troublesome, but also height of thetoroidal type continuously variable transmission in the up-and-downdirection in FIGS. 26 to 28 is increased, so that it is hard to make thetransmission compact and light-weighted. Further, if the transmission isforcibly made compact and light-weighted to permit installation of thetransmission within a limited space, strength of parts is decreased,thereby worsening endurance.

Japanese Patent Laid-Open No. 10-274300 (1998) discloses an arrangementin which pivot shafts provided on both ends of trunnions constituting atoroidal type continuously variable transmission are supported bysupport members directly secured to an inner surface of a casing. Withthis arrangement, since the number of parts is decreased, thetransmission can be made compact and light-weighted. However, in case ofthe toroidal type continuously variable transmission disclosed in thisdocument, the support members for supporting the pivot shafts providedon both ends of the trunnions are independently provided for eachtrunnion.

Thus, in the arrangement disclosed in the above Japanese PatentLaid-Open No. 10-274300, loads acting on the trunnions when the toroidaltype continuously variable transmission is driven directly act on thecasing. That is to say, when the toroidal type continuously variabletransmission is driven, since pressure acting on contact areas betweeninner surfaces of input and output discs and peripheral surfaces ofpower rollers is great, the power rollers are subjected to great thrustloads. Such thrust loads act on the support portions for the pivotshafts provided on both ends of the trunnions through the trunnions. Inthe arrangement disclosed in above-mentioned document, the great loadsacting on the pivot shafts in this way act on the casing as they are. Inmany cases, since the casing of the transmission is made of light alloysuch as aluminium alloy to reduce the weight, in order to preventdisplacement of the pivot shafts and to ensure the endurance of thecasing regardless of great loads, it is necessary to increase a wallthickness of the casing, with the result that it is hard to make thetransmission compact and light-weighted.

Further, when the toroidal type continuously variable transmission isdriven, due to the great loads acting on the trunnions from the powerrollers, the trunnions are elastically deformed so that the innersurfaces thereof becomes concave. As a result, parallelism betweencentral axes of the pivot shafts provided on the ends of the trunnionsand central axes of circular holes formed in the support members securedto the inner surface of the casing is lost more or less. In thearrangement disclosed in above-mentioned document, it is not consideredthat the trunnions can be displaced smoothly without damaging any partseven if such a condition occurs.

SUMMARY OF THE INVENTION

In consideration of the above circumstances, a toroidal typecontinuously variable transmission according to the present invention isdevised.

As is in conventional toroidal type continuously variable transmissions,a toroidal type continuously variable transmission according to thepresent invention comprises a casing, input and output discs supportedwithin the casing in coaxial with each other and capable of beingrotated independently, the even number of pivot shafts disposed incoaxial with or parallel with each other between the discs at twistedpositions where the pivot shafts do not intersect with a central axis ofthe discs but extend toward directions perpendicular to the centralaxis, a plurality of trunnions rockable around the pivot shafts,displacement shafts protruded from inner surfaces of the trunnions, aplurality of power rollers rotatably supported around the displacementshafts and interposed between inner surfaces of the input and outputdiscs, and support means provided at sides of the power roller andadapted to support the pivot shafts for rocking displacement and axialdisplacement.

Further, as is in conventional toroidal type continuously variabletransmissions, a toroidal type continuously variable transmissionaccording to the present invention comprises a casing, first and secondouter discs supported within the casing in coaxial with each other andcapable of being rotated synchronously so that inner surfaces of thediscs are opposed to each other, a first inner disc supported in coaxialwith the first and second outer discs and capable of being rotatedindependently from the first and second outer discs and having an innersurface opposed to the inner surface of the first outer disc, a secondinner disc supported in coaxial with the first inner disc and capable ofbeing rotated synchronously with the first inner disc and having aninner surface opposed to the inner surface of the second outer disc,four first pivot shafts disposed in coaxial with or parallel with eachother between the first outer disc and the first inner disc at twistedpositions where the pivot shafts do not intersect with a central axis ofthese discs but extend toward directions perpendicular to the centralaxis, a pair of first trunnions rockable around the first pivot shafts,first displacement shafts protruded from inner surfaces of the firsttrunnions, a pair of first power rollers rotatably supported around thefirst displacement shafts and interposed between the inner surface ofthe first outer disc and the inner surface of the first inner disc, foursecond pivot shafts disposed in coaxial with or parallel with each otherbetween the second outer disc and the second inner disc at twistedpositions where the pivot shafts do not intersect with a central axis ofthese discs but extend toward directions perpendicular to the centralaxis, a pair of second trunnions rockable around the second pivotshafts, second displacement shafts protruded from inner surfaces of thesecond trunnions, a pair of second power rollers rotatably supportedaround the second displacement shafts and interposed between the innersurface of the second outer disc and the inner surface of the secondinner disc, and first and second support means provided substantially inparallel with each other at sides of the first and second inner discswith the interposition of the first and second inner discs in such amanner that one ends are disposed between the first outer disc and thefirst inner disc and the other ends are disposed between the secondouter disc and the second inner disc; and the first support meanssupports two of the four first pivot shafts and two of the four secondpivot shafts for rocking movement and axial displacement, and the secondsupport means supports the other two of the four first pivot shafts andthe other two of the four second pivot shafts for rocking movement andaxial displacement.

Particularly, the toroidal type continuously variable transmissionaccording to the present invention is characterized in that membersconstituting the support means or the first and second support means aredirectly supported by and secured to an inner surface of the casing.

According to the toroidal type continuously variable transmission of thepresent invention having the above-mentioned arrangements, a rotationalforce is transmitted between the input disc or the first and secondouter discs and the output disc or the first and second inner discs,and, a speed change ratio between the input disc or the first and secondouter discs and the output disc or the first and second inner discs canbe changed in the same manner as the conventional toroidal typecontinuously variable transmissions.

Particularly, in the toroidal type continuously variable transmission ofthe present invention, since the members constituting the support meansor the first and second support means are directly supported by andsecured to the inner surface of the casing, the number of parts isreduced to facilitate manufacture, control and assembling of the parts,and a height of the toroidal type continuously variable transmission isdecreased to make the transmission compact and light-weighted whileensuring the endurance.

In a toroidal type continuously variable transmission according toanother aspect of the present invention, yokes having ends forsupporting the pivot shafts provided on the ends of the plurality oftrunnions forming a part of the support means are directly supported byand secured to the inner surface of the casing. Further, it is designedso that the pivot shafts can be displaced axially, by splines, withrespect to the ends of the yokes, and needle bearings for rockablysupporting the pivot shafts are provided within the inside of thesplines.

In a toroidal type continuously variable transmission according to afurther aspect of the present invention, yokes having four corners forsupporting the pivot shafts provided on the ends of the plurality oftrunnions forming a part of the first and second support means aredirectly supported by and secured to the inner surface of the casing.Further, it is designed so that the pivot shafts can be displacedaxially, by splines, with respect to the four corners of the yokes, andneedle bearings for rockably supporting the pivot shafts are providedwithin the inside of the splines.

In this way, in the toroidal type continuously variable transmission ofthe present invention, since the yokes constituting the support means orthe first and second support means are directly supported by and securedto the inner surface of the casing, the number of parts is reduced tofacilitate manufacture, control and assembling of the parts, and aheight of the toroidal type continuously variable transmission isdecreased to make the transmission compact and light-weighted whileensuring the endurance.

Furthermore, since the yokes support the pivot shafts provided on theends of the plurality of trunnions, all or part of forces acting on theplurality of trunnions can be canceled in the yokes. Thus, since a greatload does not act on the casing supporting the yokes, it is not requiredthat the wall thickness of the casing be increased in order to preventdisplacement of the support portions for the pivot shafts and reductionin endurance of the casing.

In addition, since the splines and the needle bearings are providedbetween the pivot shafts and the yokes, the displacement of thetrunnions with respect to the yokes can be effected smoothly andcorrectly.

It may be designed so that the splines are ball splines, and outerperipheral surfaces of outer races formed in inner peripheral surfacesof ball spline grooves constituting the ball splines are formed assemi-spherical convex surfaces, and the convex surfaces are rockablyreceiving in circular holes formed in the yokes.

Incidentally, a gear transmitting mechanism may be provided between theplurality of trunnions to synchronize the inclination movements of thetrunnions.

A toroidal type continuously variable transmission according to afurther aspect of the present invention comprises a casing, input andoutput discs supported within the casing in coaxial with each other andcapable of being rotated independently so that inner surfaces of thediscs are opposed to each other, four or more and the even number ofpivot shafts disposed in coaxial with or parallel with each otherbetween the input disc and the output disc at twisted positions wherethe pivot shafts do not intersect with a central axis of the discs butextend toward directions perpendicular to the central axis, a pluralityof trunnions rockable around the pivot shafts, displacement shaftsprotruded from inner surfaces of the trunnions, a plurality of powerrollers rotatably supported around the displacement shafts andinterposed between an inner surface of the input disc and an innersurface of the output disc, and a plurality of actuators having the samenumber as that of the trunnions and adapted to displace the trunnionsalong axial directions of the pivot shafts.

A toroidal type continuously variable transmission according to a stillfurther aspect to the present invention comprises a casing, first andsecond outer discs supported within the casing in coaxial with eachother and capable of being rotated synchronously so that inner surfacesof the discs are opposed to each other, a first inner disc supported incoaxial with the first and second outer discs and capable of beingrotated independently from the first and second outer discs and havingan inner surface opposed to the inner surface of the first outer disc, asecond inner disc supported in coaxial with the first inner disc andcapable of being rotated synchronously with the first inner disc andhaving an inner surface opposed to the inner surface of the second outerdisc, four or more and the even number of first pivot shafts disposed incoaxial with or parallel with each other between the first outer discand the first inner disc at twisted positions where the pivot shafts donot intersect with a central axis of these discs but extend towarddirections perpendicular to the central axis, a plurality of firsttrunnions rockable around the first pivot shafts, first displacementshafts protruded from inner surfaces of the first trunnions, a pluralityof first power rollers rotatably supported around the first displacementshafts and interposed between the inner surface of the first outer discand the inner surface of the first inner disc, four or more and the evennumber of second pivot shafts disposed in coaxial with or parallel witheach other between the second outer disc and the second inner disc attwisted positions where the pivot shafts do not intersect with a centralaxis of these discs but extend toward directions perpendicular to thecentral axis, a plurality of second trunnions rockable around the secondpivot shafts, second displacement shafts protruded from inner surfacesof the second trunnions, a plurality of second power rollers rotatablysupported around the second displacement shafts and interposed betweenthe inner surface of the second outer disc and the inner surface of thesecond inner disc, and a plurality of actuators having the same numberas that of the trunnions and adapted to displace the trunnions alongaxial directions of the pivot shafts.

Particularly, in the toroidal type continuously variable transmission ofthe present invention, there is provided a synchronizing mechanism formechanically synchronizing the displacement movements of the trunnionsalong the axial directions of the pivot shafts effected by theactuators.

For example, such a synchronizing mechanism may comprise receivingpieces having proximal ends secured to the ends of the trunnions andsecured to tip ends of drive rods capable of being displaced axially bythe actuators to displace the trunnions along the axial directions ofthe pivot shafts, and rocking arms having ends engaged by the receivingpieces to be merely rocked and central portions pivotally supported by asecond pivot shaft (fixed portion) arranged in parallel with arotational center line of the discs.

As is in conventional toroidal type continuously variable transmissions,in the toroidal type continuously variable transmission of the presentinvention having the above-mentioned arrangement, the rotational forceis transmitted between the input disc and the output disc or between thefirst and second outer discs and the first and second inner discs, and,further, by changing the inclination angles of the trunnions, therotational speed ratio between the discs is changed.

Particularly, in the toroidal type continuously variable transmission ofthe present invention, since the displacement movements of the trunnionsalong the axial directions of the pivot shafts effected by the actuatorsare mechanically synchronized, even when a quick speed change operationis performed, the inclination angles of the trunnions can be coincidedwith each other exactly.

The other objects and features of the present invention will be apparentfrom the following detailed explanation of the invention referring tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view corresponding to a sectional view taken alongthe line A—A in FIG. 26, showing a first embodiment of the presentinvention;

FIG. 2 is a sectional view taken along the line B—B in FIG. 1;

FIG. 3 is an enlarged sectional view showing a right portion of FIG. 1;

FIG. 4 is a view corresponding to a portion C in FIG. 1, showing acondition that assembling is being effected;

FIG. 5 is a view corresponding to a portion C in FIG. 1, showing acondition that the assembling is completed;

FIG. 6 is a view showing a condition that forces act on yokesconstituting a toroidal type continuously variable transmission ofdouble cavity type, looked at from the above in FIG. 1;

FIG. 7 is a partial sectional view corresponding to a right upperportion of FIG. 1, showing a deformed condition of a trunnion duringoperation in an exaggerated manner;

FIGS. 8A and 8B are views similar to FIG. 6, showing a condition thatforces act on yokes constituting a toroidal type continuously variabletransmission of single cavity type;

FIG. 9 is a sectional view corresponding to a sectional view taken alongthe line A—A in FIG. 26, showing a second embodiment of the presentinvention;

FIG. 10 is an enlarged view of a portion D in FIG. 9, where an areaabove a line a shows a sectional view taken along the line E-O-F in FIG.11 and an area below the line a shows sectional view taken along theline E-O-G in FIG. 11;

FIG. 11 is a view looked at from the above in FIG. 10, with a casingomitted;

FIG. 12 is a view similar to FIG. 3, showing a third embodiment of thepresent invention;

FIG. 13 is a sectional view corresponding to a sectional view takenalong the line A—A in FIG. 26, showing a fourth embodiment of thepresent invention;

FIG. 14 is a view corresponding to a portion I in FIG. 13;

FIG. 15 is a sectional view corresponding to a sectional view takenalong the line A—A in FIG. 26, showing a fifth embodiment of the presentinvention;

FIG. 16 is an enlarged view showing a portion J in FIG. 15;

FIG. 17 is a perspective view of a receiving piece;

FIG. 18 is a view looked at from the below in FIG. 15, showing amechanism for synchronizing axial displacement movements of drive rods;

FIG. 19 is a view looked at from a direction shown by arrow K in FIG.15;

FIG. 20 is a view looked at from the below in FIG. 15, showing a geartransmitting mechanism;

FIG. 21 is a substantially plan view of a toroidal type continuouslyvariable transmission, for explaining a measured portion in a testeffected to confirm an effect of the invention;

FIGS. 22A and 22B are graphs showing displacement conditions oftrunnions constituting the toroidal type continuously variabletransmission of the present invention;

FIGS. 23A and 23B are graphs showing displacement conditions oftrunnions constituting a conventional toroidal type continuouslyvariable transmission;

FIG. 24 is a side view showing a fundamental construction of aconventional toroidal type continuously variable transmission, in amaximum deceleration condition;

FIG. 25 is a side view similar to FIG. 24, in a maximum accelerationcondition;

FIG. 26 is a sectional view showing an example of a conventionalconcrete construction;

FIG. 27 is a sectional view taken along the line A—A in FIG. 26;

FIG. 28 is a sectional view taken along the Line H—H in FIG. 26;

FIG. 29 is a sectional view showing a first example of a conventionalsynchronizing mechanism using a cable; and

FIG. 30 is a sectional view showing a second example of a conventionalsynchronizing mechanism using a cable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

<First Embodiment>

FIGS. 1 to 7 show a first embodiment of the present invention.Incidentally, the characteristics of this embodiment include aconstruction of parts for supporting first pivot shafts 29 provided onboth ends of first trunnions 27 with respect to a casing 5 and aconstruction for positively synchronizing inclination angles of thetrunnions 27. Since the other constructions and functions are the sameas those of the conventional technique shown in FIGS. 26 to 28,illustration and explanation thereof are omitted or briefly described,and the characteristics of this embodiment will be mainly explained.Further, second pivot shafts 30 (FIG. 28) provided on both ends ofsecond trunnions 28 are also supported with respect to the casing 5 andinclination angles of the second trunnions 28 are positivelysynchronized by the same construction as the construction regarding thefirst pivot shafts 29. In the following explanation, as a rule, only thefirst trunnions 27 will be described, except for cases where the secondtrunnions 28 and associated parts must be explained.

A pair of yokes 54, 55 constituting first and second support means aredisposed in parallel with each other and are directly secured to opposedportions of the casing 5. Incidentally, positioning accuracy of theyokes 54, 55 with respect to the casing 5 is exactly regulated byengagement between knock pins protruded from one of the yokes and casingand lock holes formed in the other of the yokes and casing. Circularsupport holes 31 are formed in four corners of the yokes 54, 55 atengagement positions. Among these support holes 31, within the supportholes 31 formed in one ends of the yokes 54, 55, the first pivot shafts29 are supported via ball splines 56 and radial needle bearings 57 foraxial displacement and rocking movement.

Ball spline outer races 58 constituting the ball splines 56 are fittedinto opened half sides of the support holes 31 in a condition that theouter races can slightly be rocked and axial displacement of the racesis limited. To this end, the opened half sides of the support holes 31are provided with small diameter portions 59 having front diameterssmaller than rear diameters. The ball spline outer races 58 constitutingthe ball splines 56 are fitted into the smaller diameter portions 59.Outer peripheral surfaces of intermediate portions of the ball splineouter races 58 are formed as partial spherical convex surfaces 60. Aradius of curvature of each convex surface 60 is substantially equal toa half (½) of an inner diameter of each support hole 31.

Further, outwardly directed circumferential flanges 61 are formed onouter peripheral surfaces at axial one ends of the ball spline outerraces 58 and circumferential locking grooves 62 are formed in outerperipheral surfaces at the other axial ends of the ball spline outerraces. Such ball spline outer races 58 are assembled in such a mannerthat the flanges 61 are positioned at rear sides of the support holes 31and the smaller diameter portions 59 are sandwiched from both sidesbetween the flanges 61 and stop rings 63 locked to the locking grooves62. Incidentally, in this condition, a distance between each flange 61and the corresponding stop ring 63 is selected to be greater than anaxial length of the corresponding smaller diameter portion 59.Accordingly, the ball spline outer races 58 are supported within thesupport holes 31 for slight rocking movement.

Further, a plurality of outer race side ball spline grooves 64 extendingin an axial direction (up-and-down direction in FIG. 1 and FIGS. 3 to 5)are formed in an inner races 65 (also acting as outer races of theradial needle bearings 57) are disposed within the interiors of the ballspline outer races 58 in coaxial with the radial needle bearings 57.Inner race side ball spline grooves 66 extending in an axial directionare formed in portions of the outer peripheral surfaces of the ballspline inner races 65 which are opposed to the outer race side ballspline grooves 64. A plurality of balls 67 are disposed between therespective inner race side ball spline grooves 66 and the respectiveouter race side ball spline grooves 64, thereby constituting the ballsplines 56.

Cylindrical outer race tracks 68 for the radial needle bearings 57 areprovided on inner peripheral surfaces of the ball spline inner races 65.A plurality of needles 70 are disposed between the respective outer racetracks 68 and respective cylindrical inner race tracks 69 formed on theouter peripheral surfaces of the first pivot shafts 29 provided on bothends of the first trunnions 27, thereby constituting the radial needlebearings 57.

Among the first pivot shafts 29 provided on both ends of the firsttrunnions 27, tip end portions of the first pivot shafts 29 connected tothe drive rods 51 at one side (lower end side in FIGS. 1 and 3) havepinions 72 (constituting a gear transmitting mechanism 71 which will bedescribed later) secured thereto. On the other hand, circular hold-downplate 73 are secured to tip ends of the first pivot shafts 29 at theother side (upper end side in FIGS. 1 and 3) remote from the drive rods51, by threading threaded rods 74 provided on central portions of thehold-down plates into threaded holes 75 formed in the central portionsof the first pivot shafts 29. Such pinions 72 and hold-down plates 73serve to prevent axial shifting movement of the ball spline inner races65 and dislodging of the alls 67. Incidentally, dislodging of the balls67 in the opposite direction is prevented by stop rings 85 locked to theouter peripheral surfaces of proximal ends (ends near the axial centralportions of the first trunnions 27) of the ball spline inner races 65.

Incidentally, among the construction according to the illustratedembodiment, the ball spline 56 and the radial needle bearing 57 areassembled as follows. As shown in FIG. 4, the radial needle bearing 57including the ball spline inner race 65 is previously mounted on thefirst pivot shaft 29 provided on the other end of the first trunnions 27and is prevented from dislodging by means of a washer 76 and a stop ring77. Further, as shown in FIG. 4, the ball spline outer race 58 ispreviously mounted within the support hole 31 formed in the yoke 54. Inthis condition, the plurality of balls 67 constituting the ball spline56 are inserted between the respective inner race side ball splinegrooves 66 formed in the outer peripheral surface of the ball splineinner race 65 and the respective outer race side ball spline grooves 64formed in the inner peripheral surface of the ball spline outer race 58,through hole 86 formed in a portion of the casing 5 aligned with thesupport hole 31. After insertion, as shown in FIG. 5, the hold-downplate 73 is mounted, and then, the through hole 87 is closed by a lidplate 87.

By the way, in case of the toroidal type continuously variabletransmission of the present invention including the arrangementaccording to the illustrated embodiment, since the yokes 54, 55 are notdisplaced, the yokes 54, 55 do not have functions for coinciding theinclination angles of the pair of opposed first power rollers 45 witheach other. That is to say, although such inclination angles areadjusted by the axial displacement amounts of the drive rods 51controlled by supplying or discharging the pressurized oil with respectto the drive cylinders 53, it is difficult to exactly coincide theinclination angles of the pair of first power rollers 45 with each otherby such axial displacement amounts. Thus, in the conventionalarrangements, the inclination angles of the pair of first power rollers45 have been exactly coincided with each other by permitting thedisplacement of the yokes 26 a and by supporting the first power rollers45 in a so-called floating fashion. However, in the toroidal typecontinuously variable transmission of the present invention, theinclination angles of the pair of first power rollers 45 cannot becoincided with each other by the displacement of the yokes 54, 55.

Thus, in the illustrated embodiment, the pair of opposed first trunnions27 are interconnected through the gear transmitting mechanism 71 so thatthe pair of first power rollers 45 supported by the first trunnions 27can be coincided with each other exactly. To install the geartransmitting mechanism 71, one (lower one (55) in FIGS. 1 to 3) of theyokes is provided with a recessed portion 78. Accordingly, in acondition that the yoke 55 and a cylinder case 79 are overlapped witheach other, a space 80 for containing the gear transmitting mechanism 71is defined between these members 55, 79. The gear transmitting mechanism71 contained in this space 80 includes a pair of pinions 72 having thesame configuration and the same number of teeth, and a rack 81 havingtoothed portions provided on both end portions and having the samepitch. The pinions 72 are fitted onto the secured to non-cylindricalportions formed on the top ends of the first pivot shafts 29 provided onthe ends of the first trunnions 27. Accordingly, the first trunnions 27are rotated in synchronous with the pinions 72. Incidentally, when thespeed change ratio is changed, the first trunnions 27 are displaced inthe axial directions of the first pivot shafts 29. Accordingly, byproviding moderate (an amount which does not arise any problem regardingthe coincidence of the inclination angles) backlash in engagement areasbetween the pinions 72 and the rack 81, relative displacement betweenthe pinions 72 and the rack 81 is permitted.

The rack 81 can be displaced only along the axial direction (directionperpendicular to the planes of FIGS. 1 and 3) of the input shaft 1 a andis supported within the space 80. To this end, in the illustratedembodiment, the rack 81 is supported by translation rolling bearings(linear bearings) 82 for parallel shifting movement with respect to theyoke 55. That is to say, guide recessed portions 83 extending thedisplacing direction of the rack 81 are formed in a portion (opposed tothe rack 81) of a lower surface of the yoke 55 secured to the innersurface of the casing 5.

Further, guide flanges 84 are formed on portions (aligned with the guiderecessed portions 83) of an intermediate part of the rack 81. Athickness of each guide flange 84 is selected to be smaller than a widthof each guide recessed portion 83 so that the guide flanges 84 areloosely inserted within the guide recessed portions 83. The rollingbearings 82 are disposed between the respective one surfaces of theflanges 84 and the respective inner surfaces of the guide recessedportions 83. Such rolling bearings 82 are disposed at positions wherethey sandwich the flanges 84 provided on the rack from both sides (or,contrary to illustration, positions where the flanges 84 sandwich therolling bearings 82 from both sides).

Accordingly, the rack 81 can smoothly be displaced with respect to theyoke 55 with a light force without inclining toward the guide recessedportions 83. Further, if a force directing perpendicular to thedisplacing direction acts on the rack 81, any one of the pair of rollingbearings 82 of the rack 81 will support such force, thereby compensatingfor smooth displacement of the rack 81.

The pinions 72 and rack 81 supported in this way are assembled in such amanner that teeth formed on outer peripheral edges of the pinions 72 aremeshed with the toothed portions formed provided on both end portions ofthe rack 81, thereby constituting the gear transmitting mechanism 71.The gear transmitting mechanism 71 serves to minimize backlash and toincrease pitch circle diameters of the pinions 72 to some extent (withina range that can prevent interference with other members). Accordingly,the inclination angles of the first trunnions 27 to which the pinions 72are secured can exactly be coincided with the inclination angles of thefirst power rollers 45 supported by the first trunnions 27.Incidentally, although not shown, another gear transmitting mechanismhaving the same construction as the mechanism 71 is provided between thefirst trunnions 27 and the second trunnions 28 (FIG. 28) to coincide theinclination angles of the first trunnions 27 with the inclination anglesof the second trunnions 28.

As mentioned above, in the toroidal type continuously variabletransmission according to the present invention, the yokes 54, 55 asmembers constituting the first and second support means are directlysupported by an secured to the inner surface of the casing 5. Thus, theposts 33 a, 33 b (FIGS. 26 to 28) which were required for theabove-mentioned conventional arrangement can be omitted, with the resultthat the number of parts is reduced to facilitate manufacture, controland assembling of the parts, and a height of the toroidal typecontinuously variable transmission is decreased to make the transmissioncompact and light-weighted while ensuring the endurance.

In the present invention, the yokes 54, 55 support, at their fourcorners, the first and second pivot shafts 29, 30 provided on the endsof the four (in total) trunnions 27, 28 (two first trunnions 27 and twosecond trunnions 28). Thus, all of the forces acting on the first andsecond trunnions 27, 28 can be canceled within the yokes 54, 55. Now,this will be described with reference to FIG. 6. As mentioned above,when the toroidal type continuously variable transmission is driven,great thrust loads from the first and second power rollers 45, 46 act onthe first and second trunnions 27, 28 along directions shown by thearrows α in FIG. 6. Each thrust load can be divided into a forcecomponent shown by the arrow β in FIG. 6 along the diametrical directionof the first or second cavity 34 or 35 (FIG. 1) and a force componentshown by the arrow γ in FIG. 6 along the axial direction of the inputshaft 1 a.

As apparent from FIG. 6 showing such directions of forces, the forcecomponents β along the diametrical directions of the first and secondcavities 34, 35 have same magnitude and are directed in oppositedirections at the first and second trunnions 27, 28 arranged in the samecavity. Further, the force components γ along the axial direction of theinput shaft 1 a have same magnitude and are directed in oppositedirections at the first and second trunnions 27, 28 disposed in theadjacent cavities. Accordingly, all of the forces acting on the firstand second trunnions 27, 28 are canceled within the yokes 54, 55 withthe result that such forces do not act on the casing 5 supporting theyokes 54, 55. Thus, since the casing 5 is not subjected to great load,even when the wall thickness of the casing 5 is not increased so great,displacement of the support portions for the first and second pivotshafts 29, 30 can be prevented or the endurance of the casing 5 is notworsened.

Further, since the ball splines 56 and the radial needle bearings 57 aredisposed between the first pivot shafts 29 and the yokes 54, 55, thefirst trunnions 27 can be displaced smoothly and correctly with respectto the yokes 54, 55. That is to say, as apparent from the aforementionedexplanation, during the speed change operation of the toroidal typecontinuously variable transmission, the first trunnions 27 are displacedin the axial directions of the first pivot shafts 29, with the resultthat the first trunnions are rockingly displaced around the first pivotshafts 29. In the illustrated embodiment, among such displacements, theaxial displacement is effected smoothly by the ball spline 56 and therocking displacement is effected smoothly by the radial needle bearing57, with the result that the speed change operation of the toroidal typecontinuously variable transmission based on such displacements can beeffected quickly and correctly.

Further, since the outer peripheral surfaces of the ball spline outerraces 58 are formed as the semi-spherical convex surfaces 60, regardlessof elastic deformation of the first trunnions 27, edge load can beprevented from acting on the contact areas between the rolling surfacesof the needles 70 constituting the radial needle bearings 57 and theouter race track 68 and the inner race track 69. That is to say, whenthe toroidal type continuously variable transmission is driven, thegreat thrust loads act on the first power rollers 45, and, due to suchthrust loads, the first trunnions 27 are elastically deformed so thatthe opposed inner surfaces thereof become concave, as shown in FIG. 7 inan aggregated manner. Due to such elastic deformation, the central axesof the first pivot shafts 29 are slightly deviated from the central axesof the support holes 31. To cope with this, in the arrangement accordingto the illustrated embodiment, the ball spline outer races 58 arerockingly displaced within the support holes 31. The central axes of theball spline outer races 58 and the central axes of the ball spline innerraces 65 (which also act as the outer races of the radial needlebearings 57) disposed within the ball spline outer races are maintainedto be aligned with each other. In the arrangement according to theillustrated embodiment, misalignment between the central axes of thefirst pivot shafts 29 and the central axes of the support holes 31 iscompensated in this way, thereby preventing application of the edgeloads.

Further, as is in the illustrated embodiment, since the inclinationangles of the first power rollers 45 are coincided with each other bythe gear transmitting mechanism 71, great slip is prevented fromoccurring at the contact areas between the peripheral surfaces 9 a ofthe first power rollers 45 and the inner surfaces 2 a, 4 a of the discs17, 20, thereby well ensuring the efficiency of the toroidal typecontinuously variable transmission. Incidentally, although the geartransmitting mechanism 71 is effective to coincide the inclinationangles of the first power rollers 45 with each other exactly and tocoincide the inclination angles of the first power rollers 45 with andthe inclination angles of the second power rollers 46 (FIG. 28) exactly,when the present invention is carried out, a synchronizing mechanism forcoinciding the inclination angles of the first power rollers 45 with andthe inclination angles of the second power rollers 46 is not limited tothe illustrated gear transmitting mechanism 71. A synchronizingmechanism of cable type which is well known in the art and shown inFIGS. 29 and 30 may be used.

Further, the present invention is effective when it is applied to atoroidal type continuously variable transmission of double cavity type,in the points that the loads acting on the yokes can be substantiallycanceled within the yokes and the great load can be prevented fromacting on the casing supporting the yokes. However, as shown in FIGS. 24and 25, even in the toroidal type continuously variable transmission ofsingle cavity type in which the single input disc 2 and the singleoutput disc 4 are provided, a measure of effect can be expected.However, when the present invention is applied to the toroidal typecontinuously variable transmission of single cavity type, as shown inFIGS. 8A and 8B, in dependence upon the driving condition, a part ofloads acting on the trunnions 7 from the power rollers 9 may act on thecasing to which the yoke 88 is secured.

That is to say, when the rotational speed of the input disc 2 is thesame as the rotational speed of the output disc 4 (speed changeratio=1), as shown in FIG. 8A, loads having the same magnitude anddirecting in opposite directions act on the trunnions 7. Accordingly,the loads acting on the trunnions 7 are substantially canceled withinthe yoke 88, with the result that any load does not act on the casingsupporting the yoke 88. On the other hand, when the rotational speed ofthe input disc 2 differs from the rotational speed of the output disc 4(speed change ratio≠1), as shown in FIG. 8B, among the loads acting onthe trunnions 7, a load component along the axial direction of the inputdisc 2 and the output disc 4 cannot be canceled, and such load componentacts on the casing. Since the load component acting on the casing inthis way is smaller than the loads acting on the trunnions 7, when theyoke 88 is secured to the casing at plural locations, as is in thearrangement disclosed in the above Japanese Patent Laid-Open No.10-274300, unlike to the arrangement in which the loads acting on thetrunnions is transmitted to the casing as they are, there arises nopractical problem regarding prevention of deformation of the casing andassurance of endurance of the casing.

<Second Embodiment>

FIGS. 9 to 11 show a second embodiment of the present invention. Thesecond embodiment differs from the first embodiment, regarding anarrangement for supporting the first pivot shafts 29 remote from thedrive rods 51 (among the first pivot shafts 29 provided on both ends ofthe first trunnions 27) with respect to the casing 5. That is to say, inthe second embodiment, when the ball splines 56 for supporting the firstpivot shafts 29 remote from the drive rods 51 with respect to the yoke54 are assembled, the through hole 86 (FIGS. 4 and 5) used in the firstembodiment are omitted and the lid plate 87 (FIG. 5) for closing thethrough hole 86 is also omitted, thereby reducing the cost and improvingthe strength of the casing 5.

To this end, in the second embodiment, notches 89 caved in thediametrical direction of the support hole 31 are formed in diametricallyopposed positions (two positions) of the smaller diameter portion 59formed in the half part of the opened portion of the support hole 31 ofthe yoke 54. Further, protrusions 90 capable of passing through thenotches 89 are formed on diametrically opposed positions (two positions)of the outer peripheral surface of the proximal end (upper end in FIGS.9 and 10) of the ball spline outer race 58. A locking notch 91 is formedin a central portion of an outer peripheral edge of one of theprotrusions 90 (protrusion at the right in FIG. 10 and at the right andupper in FIG. 11). Further, in correspondence to the smaller diameterportion 59 of the support hole 31 formed in the yoke 54, a threaded hole92 is formed in a portion aligned with the locking notch 91 between thenotches 89, and a tip end of a set screw 93 threaded in the threadedhole 92 is engaged by the locking notch 91.

The construction according to the illustrated embodiment as mentionedabove is assembled as follows. The radial needle bearing 57 and the ballspline 56 are previously attached to the end of the first pivot shaft29. The dislodging of the plurality of balls 67 constituting the ballspline 56 is prevented by the stop ring locked to the inner peripheralsurface of the end of the ball spline outer race 58 or the outerperipheral surface of the end of the ball spline inner race 65. In acondition that the notches 89 are aligned with the protrusions 90, theprotrusions 90 are inserted into the support hole 31. Then, the ballspline outer race 58 is rotated by 90 degrees to align the locking notch91 with the threaded hole 92. Then, the set screw 93 is threaded intothe threaded hole 92 to enter the tip end of the set screw 93 into thelocking notch 91. As a result, the notches 89 are deviated from theprotrusions 90 and the ball spline outer race 58 can be maintainedwithin the support hole 31. Since the other constructions and functionsare the same as those in the first embodiment, the same elements aredesignated by the same reference numerals and duplicated explanationwill be omitted.

<Third Embodiment>

FIG. 12 shows a third embodiment of the present invention. In the thirdembodiment, rollers 94 are disposed between the outer race side ballspline grooves 64 formed in the inner peripheral surface of the ballspline outer race 58 and the inner race side ball spline grooves 66formed in the outer peripheral surface of the ball spline inner race 65,respectively. Accordingly, radial load capacity of the spline portioncan be made greater. Incidentally, the rollers 94 are not rolling as thefirst pivot shafts 29 are shifted in the axial direction. Accordingly,in the third embodiment, although the force required for shifting thefirst pivot shafts 29 becomes greater than those in the first and secondembodiments, since the axial shifting movement of the first pivot shafts29 is effected by the drive cylinder 53 (FIGS. 1 and 9) with a strongforce, so long as the diameter and oil pressure of the drive cylinder 53are reserved, adequate practical response ability can be obtained. Theother constructions and functions are the same as those in the firstembodiment.

<Fourth Embodiment>

Next, a fourth embodiment of the present invention shown in FIGS. 13 and14 will be explained. Incidentally, explanation of the same elements asthose in the previous embodiments will be omitted.

In the fourth embodiment, among support holes 131, within the supportholes 131 formed on one ends of yokes 154, 155, first pivot shafts 129are supported by radial needle bearings 136 for rocking movement andaxial displacement. Incidentally, outer peripheral surfaces of outerraces 137 constituting the radial needle bearings 136 are formed asspherical convex surfaces so that edge loads are prevented from actingon contact areas between rolling surface of needles 138 constituting theradial needle bearings 136 and associated surfaces, regardless ofelastic deformation of first trunnions 127.

That is to say, when the toroidal type continuously variabletransmission is driven, great thrust loads act on first power roller145, with the result that the first trunnions 127 are elasticallydeformed so that opposed inner surfaces thereof become concave by thethrust loads. Due to such elastic deformation, central axes of the firstpivot shaft 129 are slightly deviated from central axes of the supportholes 131. In such a case, the deviation is compensated by rocking theouter races 137 within the support holes 131, thereby preventingapplication of the edge load.

However, in case of the toroidal type continuously variable transmissionof the present invention including the construction according to theillustrated embodiment, unlike to the conventional construction shown inFIGS. 26 to 28, since the yokes 154 are not displaced, the deviationbetween the central axes of the first pivot shafts 129 and the centralaxes of the support holes 131 is limited. That is to say, in theconventional construction, the inclination angles of the pair of opposedfirst power rollers 145 are coincided with each other by supporting theyokes 126 a, 126 b for slight displacement with respect to the casing105 via the support posts 133 a, 133 b. Thus, when the toroidal typecontinuously variable transmission is driven, the central axes of thefirst pivot shaft 129 are deviated from the central axes of the supportholes 131 not only by elastic deformation of the first trunnions 127 butalso by displacement of the yokes 126 a, 126 b. Accordingly, in theconventional construction, it is inevitable that the radial needlebearings 136 are provided with the outer races 137 having sphericalconvex outer peripheral surfaces. To the contrary, in the illustratedembodiment, since the yokes 154, 155 are not displaced, as mentionedabove, the deviation between the central axes of the first pivot shafts129 and the central axes of the support holes 131 is limited.Accordingly, so long as occurrence of edge load can be prevented, forexample, by providing “crowns” on the needles 138, as shown in FIG. 14,the outer races 137 can be omitted from the radial needle bearings 136.

Further, as mentioned above, in case of the toroidal type continuouslyvariable transmission of the present invention including theconstruction according to the illustrated embodiment, since the yokes154, 155 are not displaced, the yokes do not have functions forcoinciding the inclination angles of the pair of opposed first powerrollers 145 with each other. That is to say, although the inclinationangles are adjusted by axial displacement amounts of drive rods 151controlled by supplying or discharging the pressurized oil with respectto the drive cylinders 153, it is difficult to exactly coincide theinclination angles of the pair of first power rollers 145 by such axialdisplacement amounts. Thus, in the conventional construction, theinclination angles of the pair of first power rollers 145 have beenexactly coincided with each other by permitting the displacement of theyokes 126 a and by supporting the first power rollers 145 in a so-calledfloating fashion. However, in the toroidal type continuously variabletransmission of the present invention, the inclination angles of thepair of first power rollers 145 cannot be coincided with each other bythe displacement of the yokes 154, 155. Thus, in the illustratedembodiment, the inclination angles of the pair of first power rollers145 supported by the first trunnions 127 are coincided with each otherexactly by interconnecting the pair of opposed first trunnions 127through a gear transmitting mechanism 156.

To install the gear transmitting mechanism 156, one (lower one (155) inFIG. 13) of the yokes is provided with a recessed portion 157.Accordingly, in a condition that the recessed portion 157 and a cylindercase 158 are overlapped with each other, a space 159 for containing thegear transmitting mechanism 156 is defined between these members 155,158. The gear transmitting mechanism 156 contained in this space 159includes a pair of pinions 160 having the same configuration and thesame number of teeth, an a rack 161 having toothed portions provided onboth end portions and having the same pitch. The pinions 160 are fittedonto and secured to non-cylindrical portions formed on the tip ends ofthe first pivot shafts 129 provided on the ends of the first trunnions127, or are supported by ball splines and the like for axial shiftingmovement without relative rotation. Accordingly, the first trunnions 127are rotated in synchronous with the pinions 160.

The rack 161 can be displaced only along the axial direction (directionperpendicular to the plane of FIG. 13) of an input shaft 101 a and issupported within the space 159. To this end, in the illustratedembodiment, a guide protruded portion 162 formed on a side surface ofthe rack 161 is engaged by a guide groove 163 formed in the bottom ofthe recessed portion 157. Further, a sliding protruded portion 166 isformed on the other side surface of the rack 161, and the slidingprotruded portion 166 is slid with respect to the cylinder case 158,thereby preventing the rack 161 from shifting toward a fallen direction.Incidentally, a structure for supporting the rack 161 for parallelshifting movement only in one direction is not limited to theillustrated structure, but, various structures known in the art can beused. For example, an elongated hole extending the directionperpendicular to the plane of FIG. 13 may be formed in the rack 161, anda plurality of guide pins fixed along the direction perpendicular to theplane of FIG. 13 within the space 159 may be engaged by the elongatedhole.

The pinions 160 and rack 161 supported in this way are assembled in sucha manner that teeth formed on outer peripheral edges of the pinions 160are meshed with the toothed portions formed provided on both endportions of the rack 161, thereby constituting the gear transmittingmechanism 156. The gear transmitting mechanism 156 serves to minimizebacklash and to increase pitch circle diameters of the pinions 160 tosome extent (within a range that can prevent interference with othermembers). Accordingly, the inclination angles of the first trunnions 127to which the pinions 160 are secured can exactly be coincided with theinclination angles of the first power rollers 145 supported by the firsttrunnions 127. Incidentally, although not shown, another geartransmitting mechanism having the same construction as the mechanism 156is provided between the first trunnions 127 and second trunnions 128(refer to the reference numeral 28 in FIG. 28) to coincide theinclination angles of the first trunnions 127 with the inclinationangels of the second trunnions 128.

Further, a stopper plate 164 provided at an upper central part in FIG.13 serves to prevent the inclination angles of the first trunnions 127from becoming too great and is disposed around a nozzle from 165 forsupplying lubricating oil to contact areas between peripheral surfaces109 a of the first power rollers 145 and inner surfaces 102 a of a firstinput disc 117 and inner surface 104 a (FIG. 26) of a first output disc120. Incidentally, in the above explanation, an example that the presentinvention is applied to the toroidal type continuously variabletransmission of double cavity type was described. The present inventioncan achieve remarkable effect when it is applied to the toroidal typecontinuously variable transmission of double cavity type, the presentinvention can also be applied to a toroidal type continuously variabletransmission of single cavity type as shown in FIGS. 24 and 25.

As mentioned above, in the toroidal type continuously variabletransmission according to the present invention, the yokes 154, 155 asmembers constituting the first and second support means are directlysupported by and secured to the inner surface of the casing 105. Thus,the posts 133 a, 133 b which were required for the above-mentionedconventional arrangement can be omitted and the outer races 137constituting the radial needle bearings 136 can also be omitted, withthe result that the number of parts is reduced to facilitatemanufacture, control and assembling of the parts, and a height of thetoroidal type continuously variable transmission is decreased to makethe transmission compact and light-weighted while ensuring theendurance. Further, as is in the illustrated embodiment, since theinclination angles of the first power rollers 145 are coincided witheach other by the gear transmitting mechanism 156, considerable slip canbe prevented from occurring in the contact areas between the peripheralsurfaces 109 a of the first power rollers 145 and inner surfaces 102 a,104 a of the discs, thereby well ensuring the efficiency of the toroidaltype continuously variable transmission.

Since the present invention has the above-mentioned arrangement andfunction, a toroidal type continuously variable transmission which canbe manufactured cheaply with compact and light-weighted and which hasexcellent transmitting efficiency can be provided.

<Fifth Embodiment>

Now, a fifth embodiment of the present invention will be described.

The above-mentioned gear transmitting mechanism 71 (or 156) is designedin consideration of the fact that the inclination angels of thetrunnions and accordingly the power rollers caused by the axialdisplacement of the drive rods 51 (or 151) are coincided with eachother, but is not intended to synchronize the axial displacements of thedrive rods 51 themselves. The axial displacements of the drive rods 51are synchronized by controlling the oil pressure introduced into thedrive cylinders 53. Thus, in the transition immediately after the speedchange operation is started, the inclination angles of the trunnions 27,28 differ from each other delicately, and, as the case may be, slid mayoccur in the contact areas between the peripheral surfaces 9 a of thepower rollers 45, 46 and the inner surfaces 2 a, 4 a of the discs 2, 4,17, 18, 20, 21.

The slip generated in the contact areas for this reason is apt to occurwhen the trunnions 27, 28 are quickly shifted in the axial directions ofthe pivot shafts 29, 30 in order to effect the speed change operationquickly. If the slip is generated, since not only the power transmittingefficiency is worsened but also life of rolling fatigue of each surfaceis shortened, the occurrence of the slip is not preferable. In order topermit the quick speed change operation while preventing thetransmitting efficiency from worsening and the life of rolling fatiguefrom shortening, it is necessary to realize a structure in which theaxial displacements of the drive rods 51 themselves are synchronizedwith each other exactly.

A toroidal type continuously variable transmission according to thefifth embodiment is devised in consideration of the above circumstances.

FIGS. 15 to 20 show the fifth embodiment of the present invention.Incidentally, this embodiment is characterized in that it has a specificconstruction for positively synchronizing inclination angles of firsttrunnions 227 with inclination angles of second trunnions 228 (refer toreference numeral 28 in FIG. 28) and a specific construction forsupporting first pivot shafts 229 provided on both ends of the firsttrunnions 227 and second pivot shafts 230 (refer to reference numeral 30in FIG. 28) provided on both ends of the second trunnions 228. Since theother constructions and functions are the same as those of theconventional technique shown in FIGS. 26 to 28, illustration andexplanation of the similar elements are omitted or simplified, and thecharacteristics of this embodiment will be described mainly.

A pair of yokes 258, 259 are directly secured to opposed portions of thecasing 205. Circular support holes 231 are formed in four corners of theyokes 258, 259 at areas aligned with each other. Within the supportholes 231, the first pivot shafts 229 are supported via ball splines 260and radial needle bearings 261 for axial displacement and rockingmovement.

Ball spline outer races 262 constituting the ball splines 260 are fittedinto the support holes 231 in a condition that the axial displacement ofthe races is limited. A plurality of outer race side ball spline grooves263 extending in an axial direction (up-and-down direction in FIGS. 15and 16) are formed in inner peripheral surfaces of the ball spline outerraces 262. And, ball spline inner races 264 (also acting as outer racesof the radial needle bearings 261) are disposed within the interiors ofthe ball spline outer races 262 in coaxial with the radial needlebearings 261. Inner race side ball spline grooves 265 extending in anaxial direction are formed in portions of the outer peripheral surfacesof the ball spline inner races 264 which are opposed to the outer raceside ball spline grooves 263. A plurality of balls 266 are disposedbetween the respective inner race side ball spline grooves 265 and therespective outer race side ball spline grooves 263, thereby constitutingthe ball splines 260. Incidentally, any play of the ball spline outerraces 262 is prevented by elastic members such as coned disc springs290.

Cylindrical outer race tracks 267 for the radial needle bearings 261 areprovided on inner peripheral surfaces of the ball spline inner races264. A plurality of needles 269 are disposed between the respectiveouter race tracks 267 and respective cylindrical inner race tracks 268formed on the outer peripheral surfaces of the first pivot shafts 229provided on both ends of the first trunnions 227, thereby constitutingthe radial needle bearings 261.

Drive rods 251 having proximal ends (upper ends in FIG. 15) connected toone ends of lower first pivot shafts among the first pivot shafts 229provided on both ends of the first trunnions 227 extends throughthrough-holes 271 formed in a valve body 270 secured to the casing 205.Receiving pieces 272 as shown in FIG. 17 are secured to tip ends (lowerends in FIG. 15) of the drive rods 251 protruded from an outer surface(lower surface in FIG. 15) of the valve body 270. The receiving pieces272 are constituted by circumferential parts of peripheral edges of apair of parallel ring portions 273 a, 273 b via a partial cylindricalconnecting portion 274, and an opening portion 275 is defined byportions deviated from the connecting portion 274. Among the ringportions 273 a, 273 b, an inner diameter of one (upper one in FIGS. 15and 17) ring portion 273 a is relatively small so that only a malethreaded portion formed on the drive rod 251 can pass through such aring portion. On the other hand, an inner diameter of the other (lowerone is FIGS. 15 and 17) ring portion 273 b is relatively great so that anut 276 to be threaded onto the male threaded portion and a tool fortightening the nut 276 can pass through such a ring portion.

Pivot brackets 279 having second pivot shafts 278 are provided onattachment substrate plates 277 secured to the outer surface of thevalve body 270. The second pivot shafts 278 extend in parallel withrotational axes of first and second input discs 217 and first and secondoutput discs 220, 221 (FIG. 12) and are disposed at positions opposed tosides of first and second cavities 234, 235 (FIG. 12). The second pivotshafts 278 rockably support width-wise (left-and-right direction in FIG.18) central portions of both longitudinal (up-and-down direction in FIG.18) ends of a rocking arm 280 formed as a substantially square frame asshown in FIG. 18. Accordingly, both width-wise ends of the rocking arm280 are displaced in opposite directions by the same amount with respectto the axial direction of the drive rods 251.

The both longitudinal ends of both width-wise ends of the rocking arm280 are engaged by the opening portion 275 between the pair of ringportions 273 a, 273 b constituting the receiving pieces 272 so that anyplay is not generated even when the rocking arm is rocked around thesecond pivot shafts 278. To this end, in the illustrated embodiment,small projections 281 are formed on areas of both surfaces of the bothlongitudinal ends of both width-wise ends of the rocking arm 280 whichare opposed to the ring portions 273 a, 273 b, and tip ends of the smallprojections 281 abut against opposed surfaces of the ring portions 273a, 273 b. Accordingly, axial displacements (along the axial directionsof the first and second pivot shafts 229, 230) of the receiving pieces272 and of the first and second trunnions 227, 228 fixedly connected tothe receiving pieces 272 via the drive rods 25 a are mechanicallysynchronized exactly. Incidentally, a precess cam is secured to anytrunnion or the drive rod fixedly connected to any trunnions so thatfeedback control for activating a control valve for supplying ordischarging pressurized oil with respect to the drive cylinders 253 iseffected by the precess cam.

Further, in the illustrated embodiment, the first and second trunnions227, 228 are interconnected by a gear transmitting mechanism 282. Toinstall the gear transmitting mechanism 282, one (lower one (259) inFIG. 15) of the yokes is provided with a recessed portion 284.Accordingly, in a condition that the yoke 259 and a cylinder case 285are overlapped with each other, a space 289 for containing the geartransmitting mechanism 282 is defined between these members 259, 285.The gear transmitting mechanism 282 contained in this space 289 includesa pair of pinions 283 having the same configuration and the same numberof teeth, and four racks 287 a, 287 b having toothed portions providedon both end portions and having the same pitch. The pinions 283 arefitted onto and secured to non-cylindrical portions formed on the tipends of the first and second pivot shafts 229, 230 provided on the endsof the first and second trunnions 227, 228. Accordingly, the first andsecond trunnions 227, 228 are rotated in synchronous with the pinions283. Incidentally, when the speed change ratio is changed, the first andsecond trunnions 227, 228 are displaced in the axial directions of thefirst and second pivot shafts 229, 230. Accordingly, by providingmoderate (an amount which does not arise any problem regarding thecoincidence of the inclination angles) backlash in engagement areasbetween the pinions 283 and the racks 287 a, 287 b, relativedisplacement between the pinions 283 and the racks 287 a, 287 b ispermitted.

The racks 287 a, 287 b can be displaced only along the axial direction(direction perpendicular to the plane of FIG. 15 or left-and-rightdirection in FIG. 15; left-and-right direction or up-and-down directionin FIG. 20) of the input shaft 1 a and are supported within the space289. To this end, in the illustrated embodiment, the racks 287 a, 287 bare supported by pairs of translation rolling bearings (linear bearings)288 for parallel shifting movement with respect to the yokes 259.Accordingly, the racks 287 a, 287 b can smoothly be displaced with alight force without inclination. Further, if a force directingperpendicular to the displacing direction acts on the racks 287 a, 287b, any one of the pair of rolling bearings 288 of the racks 287 a, 287 bwill support such force, thereby compensating for smooth displacement ofthe racks 287 a, 287 b.

The pinions 283 and racks 287 a, 287 b supported in this way areassembled in such a manner that teeth formed on outer peripheral edgesof the pinions 283 are meshed with the teeth formed provided on both endportions of the racks 287 a, 287 b, thereby constituting the geartransmitting mechanism 282. The gear transmitting mechanism 282 servesto minimize backlash and to increase pitch circle diameters of thepinions 283 to some extent (within a range that can prevent interferencewith other members). Accordingly, the inclinations angles of the firstand second trunnions 227, 228 to which the pinions 283 are secured canexactly be coincided with the inclination angles of the first and secondpower rollers 245, 246 supported by the first and second trunnions 227,228.

As mentioned above, in the toroidal type continuously variabletransmission of the present invention, the displacements of the firstand second trunnions 227, 228 along the axial directions of the firstand second pivot shafts 229, 230 are mechanically synchronized with eachother exactly by the rocking arm 280. Accordingly, during the speedchange operation, the displacement amounts of the first and secondtrunnions 227, 228 are coincided with each other quickly and exactly,with the result that, during the speed change operation, any slip can beprevented from generating in the contact areas between the innersurfaces 202 a, 204 a (FIG. 26) of the first and second input discs 217,218 and the first and second output discs 220, 221 and the peripheralsurfaces 209 a (FIGS. 15, 27 and 28) of the first and second powerrollers 245, 246.

A result of tests effected for ascertaining the effect of the presentinvention regarding this will now be explained with reference to FIGS.22A to 23B. The tests were carried out by using the toroidal typecontinuously variable transmission of double cavity type in which a pairof power rollers are provided for each of the cavities, as shown in FIG.21. In the tests, regarding four trunnions 227, 228 supporting frontright (FR) and front left (FL) power rollers near the pressing device210 and rear right (RR) and rear left (RL) power rollers remote from thepressing device, respectively (i.e., supporting four (in total) powerrollers 245, 246), during the speed change operation, the axialdisplacement amounts and rocking angles of the trunnions 227, 228 causedafter predetermined pressurized oil was introduced into the drivecylinders were measured in connection with elapsed time. FIGS. 22A and22B show a test result of the toroidal type continuously variabletransmission of the present invention, where FIG. 22A shows the axialdisplacement amounts of the trunnions, and FIG. 22B shows the rockingangles of the trunnions. FIGS. 23A and 23B show a case where thedisplacements of the trunnions were adjusted only by adjusting the oilpressure, where FIG. 23A shows the axial displacement amounts of thetrunnions, and FIG. 23B shows the rocking angles of the trunnions. Asapparent from FIGS. 22A to 23B showing the test results, according tothe present invention, even when the quick speed change operation iseffected, the displacements of the trunnions can positively besynchronized with each other.

Further, in the toroidal type continuously variable transmissionaccording to the illustrated embodiment, the yokes 258, 259 constitutingthe first and second support means are directly supported by and securedto the inner surface of the casing 205. Thus, the support posts 233 a,233 b (refer to reference numerals 33 a, 33 b in FIGS. 27 and 28) whichwere required in the conventional arrangement can be omitted, with theresult that the number of parts is reduced to facilitate manufacture,control and assembling of the parts, and a height of the toroidal typecontinuously variable transmission is decreased to make the transmissioncompact and light-weighted while ensuring the endurance.

Further, since the ball splines 260 and the radial needle bearings 261are disposed between the first pivot shafts 229 and the yokes 258, 259,the displacements of the first and second trunnions 227, 228 withrespect to the yokes 258, 259 can be effected smoothly and correctly.That is to say, as apparent from the aforementioned explanation, duringthe speed change operation of the toroidal type continuously variabletransmission, the first and second trunnions 227, 228 are displacedalong the axial directions of the first and second pivot shafts 229,230, with the result that the trunnions are rockingly displaced aroundthe first and second pivot shafts 229, 230 due to the axialdisplacements. In the illustrated embodiment, among these displacements,the axial displacements are effected smoothly by the ball splines 260and the rocking displacements are effected smoothly by the radial needlebearings 261, so that the speed change operation of the toroidal typecontinuously variable transmission based on such displacement can beeffected quickly and correctly.

Further, as is in the illustrated embodiment, since the geartransmitting mechanism 282 is provided, even if an oil pressuresupplying circuit for the drive cylinders 252 is damaged, theinclination angels of the first and second power rollers 245 can becoincided with each other. Thus, even in malfunction, any severe slipcan be prevented from generating in the contact areas between theperipheral surfaces 209 a of the first and second power rollers 245 andthe inner surfaces 202 a, 204 a of the discs 217, 218, 220, 221, therebypreventing damage of the toroidal type continuously variabletransmission.

Since the present invention has the above-mentioned construction andfunction, the quick speed change operation can be effected whileensuring the endurance, and, thus, possibility of application of thetoroidal type continuously variable transmission to high abilityvehicles such as sports cars is increased. Therefore, the presentinvention contributes to practical use of toroidal type continuouslyvariable transmissions.

Incidentally, when the present invention is carried out, a mechanism forcoinciding the inclination angles of the trunnions with each other isnot limited to the gear transmitting mechanisms 282, 71, 156, but, amechanism using a cable as shown in FIGS. 29 and 30 may be used.

Now, a conventional synchronizing mechanism using a cable will bedescribed with reference to FIGS. 29 and 30.

That is to say, such mechanism are well-known as disclosed in JapanesePatent Laid-Open Nos. 63-67458 (1988) and 4-327051 (1992) and JapaneseUtility Model Laid-Open No. 62-200852 (1987). Among them, FIGS. 29 and30 show two examples disclosed in the Japanese Patent Laid-Open No.4-327051. On the basis of FIGS. 29 and 30, a mechanism for synchronizingthe rocking movements of the first and second trunnions 227, 228 in thetoroidal type continuously variable transmission of double cavity typewith each other will now be explained.

In order to construct the synchronizing mechanism, pulleys 354 aresecured to the axial (direction perpendicular to the planes of FIGS. 29and 30) ends of the first and second trunnions 227, 228. Peripheralsurfaces of the pulleys 354 are formed as arc surfaces coaxial with thepivot shafts 329, 330 (refer to reference numerals 29, 30 in FIGS. 27and 28). Portions of cable 355, 355 a, 355 b are fitted into and woundaround grooves formed in the peripheral surfaces of the pulleys 354 sothat four (in total) first and second trunnions 227, 228 are rocking ina synchronous manner. That is to say, in any arrangements, each cable355 is extends between the wound around the pair of pulleys 354 securedto the ends of the of first and second trunnions 227, 228 constitutingeach pair in a cross belting fashion. Accordingly, the pair of first andsecond trunnions 227, 228 (located within the same cavity) can berotated in opposite direction by the same angle, and the pulleys 354arranged along a diagonal line (located within different cavities andsituated at diametrically opposed position with respect to the inputshaft 301 a) can be rotated in the same direction by the same amount.

To this end, in the arrangement according to the first example shown inFIG. 29, the cable 355 a is mounted only between the pulleys 354arranged along the diagonal line, and the cable 355 a is secured to thepulleys 354 arranged along the diagonal line by fasteners 356. On theother hand, in the arrangement according to the second example shown inFIG. 30, the cable 355 b are wound around all of the pulleys 354, andthe cable 355 b is secured to only the pair of pulleys 354 arrangedalong the diagonal line by fasteners 356. Any slip can be generatedbetween the remaining pulleys 354 and the cable 355 b so that themovement of the cable 355 b is not transmitted to the remaining pulleys354. The arrangement shown in FIG. 30 is adopted in order to preventinterference between the cable 355 b and other members constituting thetoroidal type continuously variable transmission such as first andsecond output discs 320, 321 and large diameter output gear 323.Incidentally, also in the toroidal type continuously variabletransmission of so-called single cavity type in which a single inputdisc and a single output disc are provided, by providing the cable 355of cross belting type shown in FIGS. 29 and 30, the rocking movements ofthe plurality of trunnions are synchronized with each other. Further,although not shown, Japanese Utility Model Publication No. 4-52512(1992) and Japanese Patent Laid-Open Nos. 6-117515 (1994) and 7-243496(1995) disclose techniques in which a mechanism for synchronizinginclination angles of a plurality of trunnions with each other isconstituted by a gear transmitting mechanism.

Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. A toroidal type continuously variable transmission comprising: a casing; input and output discs supported within said casing coaxially with each other and capable of being rotated independently; an even number of pivot shafts disposed coaxially with or parallel with each other between said discs at twisted positions where said pivot shafts do not intersect with a central axis of said discs but extend toward directions perpendicular to said central axis; a plurality of trunnions rockable around said pivot shafts; displacement shafts protruded from inner surfaces of said trunnions; a plurality of power rollers rotatably supported around said displacement shafts and interposed between inner surfaces of said input and output discs; and support structure provided at sides of said power rollers and adapted to support said pivot shafts for rocking displacement and axial displacement; and wherein yokes forming a part of said support structure and having ends for supporting said pivot shafts provided on the ends of said plurality of trunnions are directly supported by and secured to an inner surface of said casing, and, said pivot shafts can be displaced axially, by splines, with respect to the ends of said yokes, and needle bearings for rockably supporting said pivot shafts are provided within the inside of said splines.
 2. A transmission according to claim 1, wherein said splines are ball splines, and outer peripheral surfaces of outer races of said ball splines are formed as semi-spherical convex surfaces, and the convex surfaces are rockably received in circular holes formed in said yokes.
 3. A transmission according to claim 2, wherein a gear transmitting mechanism is provided between said plurality of trunnions to synchronize inclination movements of said trunnions.
 4. A transmission according to claim 3, wherein said gear transmitting mechanism is a rack-and-pinion mechanism.
 5. A transmission according to claim 1, wherein a gear transmitting mechanism is provided between said plurality of trunnions to synchronize inclination movements of said trunnions.
 6. A transmission according to claim 1, the input and output discs being of half-toroidal construction.
 7. A toroidal type continuously variable transmission comprising: a casing; first and second outer discs supported within said casing coaxially with each other and capable of being rotated synchronously in a condition that inner surfaces of said discs are opposed to each other; a first inner disc supported coaxially with said first and second outer discs and capable of being rotated independently from said first and second outer discs and having an inner surface opposed to the inner surface of said first outer disc; a second inner disc supported coaxially with said first inner disc and capable of being rotated synchronously with said first inner disc and having an inner surface opposed to the inner surface of said second outer disc; four first pivot shafts disposed coaxially with or parallel with each other between said fist outer disc and said first inner disc at twisted positions where said pivot shafts do not intersect with a central axis of said discs but extend toward directions perpendicular to the central axis; a pair of first trunnions rockable around said first pivot shafts; first displacement shafts protruded from inner surfaces of said first trunnions; a pair of first power rollers rotatably supported around said first displacement shafts and interposed between the inner surface of said first outer disc and the inner surface of said first inner disc; four second pivot shafts disposed coaxially with or parallel with each other between said second outer disc and said second inner disc at twisted positions where said pivot shafts do not intersect with a central axis of said discs but extend toward directions perpendicular to the central axis; a pair of second trunnions rockable around said second pivot shafts; second displacement shafts protruded from inner surfaces of said second trunnions; a pair of second power rollers rotatably supported around said second displacement shafts and interposed between the inner surface of said second outer disc and the inner surface of said second inner disc; and first and second support structures provided substantially in parallel with each other at sides of said first and second inner discs with the interposition of said first and second inner discs in such a manner that one ends are disposed between said first outer disc and said first inner disc and the other ends are disposed between said second outer disc and said second inner disc; and wherein said first support structure supports two of said four first pivot shafts and two of said four second pivot shafts for rocking movement and axial displacement, and said second support structure supports the other two of said four first pivot shafts and the other two of said four second pivot shafts for rocking movement and axial displacement; and further wherein yokes constituting said first and second support structures and having four corners for supporting said pivot shafts provided on the ends of said plurality of trunnions are directly supported by and secured to an inner surface of said casing, and said pivot shafts can be displaced axially, by splines, with respect to said four corners of said yokes, and needle bearings for rockably supporting said pivot shafts are provided within the inside of said splines.
 8. A transmission according to claim 7, wherein said splines are ball splines, and outer peripheral surfaces of outer races of said ball splines are formed as semi-spherical convex surfaces, and the convex surfaces are rockably received in circular holes formed in said yokes.
 9. A transmission according to claim 7, wherein a gear transmitting mechanism is provided between said plurality of trunnions to synchronize inclination movements of said trunnions.
 10. A transmission according to claim 7, the input and output discs being of half-toroidal construction. 